MySQL用很多常用的內置變量，掌握這些內置變量后對于我們快速獲取當前MySQL的配置有很大幫助，下面就來列舉幾個常用的變量。

查看當前MySQL版本號信息。show variables like 'version';

MariaDB [(none)]> show variables like 'version';

+---------------+----------------+

| Variable_name | Value |

+---------------+----------------+

| version | 5.5.60-MariaDB |

+---------------+----------------+

1 row in set (0.00 sec)

查看當前MySQL服務監聽的端口號信息。show variables like 'port';

MariaDB [(none)]> show variables like 'port';

+---------------+-------+

| Variable_name | Value |

+---------------+-------+

| port | 3306 |

+---------------+-------+

1 row in set (0.00 sec)

查看當前MySQL數據的默認存儲路徑信息。show variables like 'datadir';

MariaDB [(none)]> show variables like 'datadir';

+---------------+-----------------+

| Variable_name | Value |

+---------------+-----------------+

| datadir | /var/lib/mysql/ |

+---------------+-----------------+

1 row in set (0.00 sec)

查看當前MySQL使用的引擎信息。show variables like 'storage_engine';

MariaDB [(none)]> show variables like 'storage_engine';

+----------------+--------+

| Variable_name | Value |

+----------------+--------+

| storage_engine | InnoDB |

+----------------+--------+

1 row in set (0.01 sec)

查看當前MySQL的最大連接數信息。show variables like 'max_connections';

MariaDB [(none)]> show variables like 'max_connections';

+-----------------+-------+

| Variable_name | Value |

+-----------------+-------+

| max_connections | 151 |

+-----------------+-------+

1 row in set (0.00 sec)

修改max_connectionis變量值：

MariaDB [(none)]> set global max_connections=65535;

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> show variables like 'max_connections';

+-----------------+-------+

| Variable_name | Value |

+-----------------+-------+

| max_connections | 65535 |

+-----------------+-------+

1 row in set (0.00 sec)

掌握一些必要的變量后發現在使用過程中修改，是不用重啟MySQL服務的，這樣我們可以先進入MySQL將最大連接數進行修改，后續加入到配置文件中，選擇維護時間將MySQL重啟，配置就可以永久生效了。